Salts of 1, 1, 2, 5, 6, 6-hexacyano-3, 4-diazahexadiene



United rates 7 Claims. (Cl. 260-391) This invention is concerned with anew acidic organic compound and its salt which are useful as dyes.

In the manufacture of synthetic dyes, the cost of the dye is frequentlydependent on the number of chemical steps required for its synthesis.Accordingly, dyes of relatively simple structure which can be preparedwith a minimum of chemical operations represent a desirable goal becauseof their potential economy in cost.

This invention has as an object the preparation of new dyes. A furtherobject is the preparation of components for printing and hectographinks. Other objects will appear hereinafter.

These objects are accomplished by the present invention of1,1,2,5,6,6-hexacyano-3,4-diazahexadiene and its salts, and of a processfor their preparation by the reaction of tetracyanoethylene withhydrazine. In this reaction two moles of tetracyanoethylene react withone mole of hydrazine and two moles of a base selected from the groupconsisting of hydrazine, quaternary ammonium hydroxides, alkali metalhydroxides and alkaline earth metal hydroxides. When hydrazine alone isemployed, the primary product is the dihydrazonium salt of 1,l,2,5,6,6-hexacyano-3,4-diazahexadiene. When the other bases are employed, theprimary product is the corresponding quaternary ammonium, alkali metalor alkaline earth metal salt ofl,1,2,5,6,6-hexacyano-3,4-diazahexadiene. These salts are soluble andhighly ionized in aqueous solution, and from such solutions other saltsof 1,i,2,5,6,6- hexacyano-3,4-diazahexadiene may be prepared bymetathesis.

In naming the compounds of this invention, the anion obtained on removalof the two protons from 1,1,2,5,6,6- hexacyano-3,4-diazahexadiene iscalled the l,1,2,5,6,6- hexacyano-3,4-diazahexadienediide ion.

1,1,2,5,6,6-hexacyano-3,4-diazahexadiene and its salts are coloredcompounds which are useful as dyes.1,1,2,5,6,6-hexacyano-3,4-diazahexadiene has not been isolated in thedry state. Acid conditions, such as treatment with the acidicion-exchange column or addition of a mineral acid, which are necessaryto regenerate the free compound from an aqueous solution of one of itssalts, produce decomposition of the free compound.

The l,1,2,5,6,6-hexacyano-3,4-diazahexadienediide ion is capable ofexisting in many resonance forms in which the two charges are visualizedas associated with various atoms in the molecule. It is probable thatsolutions of this ion contain an equilibrium mixture of at least some ofeach of the possible resonance forms. Some of these resonance forms arevisualized as follows:

CN (IN ON ON CN ON ON ON 2. salabl a. l=LNeN=l l CN CN 3N IN I I CN CNCN C=N ON CN CN CN l- =N N=l .l l=leN Nel= a N a a.

ice

In a preferred embodiment of this invention, two molecular equivalentsof tetracyanoethylene are added to a cold aqueous solution containingone molecular equivalent of hydrazine and at least two molecularequivalents of a base as defined above. For example the base may behydrazine, tetraethylammonium hydroxide or the hydroxide of lithium,sodium, potassium rubidium, cesium, calcium, strontium, or barium. Thismixture is stirred vigorously and the reaction is complete when all thetetracyanoethylene has disappeared into solution. The resulting solutioncontains the disubstituted salt of the base, with1,1,2,5,6,6hexacyano-3,4-diazahexadiene. This salt is isolated byevaporation of the solution. Other salts are prepared by methaesis withsuitable cationic compounds as shown in Example V.

Tetracyanoethylene for use in this invention can be prepared by thereaction of malononitrile with an equimolar quantity of sulfurmonochloride, suitably in refluxing chloroform. The tetracyanoethyleneformed can be recovered by evaporation of the chloroform solution andpurified by sublimation.

The following examples in which parts are by weight are illustrative ofthe invention.

EXAMPLE I H yarazonium 1,1,2,5,6,6-hexacyan0-3,4-a'iazahexadienea'iide Asolution of 103 parts of hydrazine hydrate in 1000 parts of water ismixed rapidly with cooling with 128 parts of powderedtetracyanoethylene. Within 10-l5 minutes solution is complete and thereis obtained a yellow-brown solution of hydrazonium1,1,2,5,6,6-hexacyano-3,4-diazahexadienediide in water.

EXAMPLE II Tetraethylammonium 1,1,2,5,6,6-hexacyan0-3,4-diazahexadz'enediide To the aqueous solution of'hydrazonium l,l,2,5,6,6- hexacyano-3,4-diazahexadienediide prepared asin Example I there is added 210 parts of tetraethylammonium bromide andthe mixture is stirred at room temperature until all the bromide isdissolved. The solution is cooled in an ice bath, and the orange-brownprecipitate which forms is collected on a filter, washed with water andrecrystallized from ethanol. There is obtained parts oftetraethylammonium l,1,2,5,6,6-hexacyano-3,4-diazahexadienediide in theform of orange needles. The product is again recrystallized from alcoholto give orange-red needles, M. P. 137-138 C.

Analysis.-Calculated for C H N C, 63.38%; H, 8.18%; N, 28.43%. Found: C,63.47%, 63.24%; H, 8.30%, 8.11%; N, 28.24%.

The light absorption spectrum of an acetone solution of this salt showsmaxirna at 456 millimicrons (molecular extinction coefiicient 15,200)and at 478 millimicrons (molecular extinction coeflicient 14,500).

EXAMPLE III Trimethylbenzylammonium I,1,2,5,6,6-hexacyan0-3,4-diazahexadienediide Ten parts of tetraethylammonium1,1,2,5,6,6-hexacyano-3,4-diazahexadienediide is dissolved in 500 partsof hot water and a solution of 20 parts of trimethylbenzylammoniumchloride in 200 parts of water is added. The orange precipitate whichforms upon cooling is collected on a filter, washed with water andrecrystallized from water. There is obtained 7 parts oftrimethylbenzylammonium 1,1,2,5,6,6-hexacyano-3,4-diazahexadienediide inthe form of orange plates, M. P. 178 C.

Analysis-Calculated for C H N C, 67.64%; H,

. 3 6.06%; N, 26.30%. Found: C, 67.55%, 67.41%; H, 6.23%, 6.02%; N,26.23%, 26.41%.

EXAMPLE IV Silver I,l,2,5,6,6-hexacyan-3,4-diazahexadienediide Twohundred fifty parts of a solution of silver nitrate in water is added toa solution of parts of tetraethylammonium 1,1,2,5,6,6-hexacyano 3,4diazahexadienediide in 500 parts of hot water. The red precipitate whichforms is collected on a filter and washed with water. There is obtained9 parts of silver l,1,2,5,6,6-hexacyano-3,4-diazahexadienediide in theform of red powder which decomposes without melting at about 250 C.

Analysis.--Calculated for Ag C N Ag, 48.17%; C, 26.81%; N, 25.02%.Found: Ag, 48.27; C, 27.06%; N, 24.67%.

EXAMPLE V A solution of hydrazine1,1,2,5,6,6-hexacyano-3,4-diazahexadienediide is prepared as in ExampleI using about half the stated amount of water (i. e., 500 parts). Asaturated aqueous solution of barium iodide is added to this. Part ofthe barium l,1,2,5,6,6-hexacyano-3,4- diazahexadienediide which isformed is precipitated and is collected by filtration and dried. Theaqueous filtrate is a solution of barium1,l,2,5,6,6-hexacyano-3,4-diazahexadienediide. This is useful in thepreparation of other 1,1,2,5,6,6-hexacyano-3,4-diazahexadienediide saltsby reaction with aqueous solutions of the corresponding sulfate. Bariumsulfate precipitates quantitatively as by product and is readilyfiltered off, leaving an aqueous solution of the1,1,2,5,6,6-hexacyano-3,4-diazahexadienediide salt of the cation whichwas introduced in the form of its sulfate. In this way, barium1,1,2,5,6,6-hexacyano- 3,4-diazahexadienediide reacts with aqueoussolutions of the sulfates of Al, Ce, Cs, Cr++, Cr+ Co Co Cu++, Fe++,Fe+++, Ga, In, Ni++, Li, K, Mn++, Rb, Sn++, Sn++++, Th, U0 V0, Zn, Zr,NHU, C H NH (C H NH (CH NH+ and (CH S+ to yield the corresponding metal,amine or sulfonium salts of 1,1,2, 5,6,6-hexacyano-3,4-diazahexadiene.lated as crystalline solids by evaporation of the solutions.

The readily soluble salts of 1,1,2,5,6,6-hexacyano-3,4- diazahexadiene,such as the hydrazonium, tetramethylammonium, sodium and potassiumsalts, react with aqueous solutions of basic dyes to precipitate thecorresponding salts which are useful as printing inks and hectographinks. Thus tetraethylammonium 1,l,2,5,6,6-hexacyano-3,4-diazahexadienediide reacts with an aqueous solution of crystalviolet to form a precipitate to the crystal violet1,1,2,5,6,6-hexacyano-3,4-diazahexadienediide salt which is a dark,almost black pigment. This is dissolved in ethanol to give a hectographink. Other basic dyes, such as methyl violet, rosaniline, and the like,react with 1,1,2, 5,6,6-hexacyano-3,4-diazahexadienediide salts to givethe corresponding dye salts which have low solubility in water and areuseful as pigments and, in alcohol solutions, as hectograph inks.

The salts are iso- In the use of1,1,2,5,6,6-hexacyano-3,4-diazahexadiene compounds of this invention asdyes, a fabric, e. g., wool, silk, nylon etc. containing amino and/ oramido groups, is immersed for a few minutes in a boiling aqueoussolution or dispersion of the compound (for example, hydrazonium1,1,2,5,6,6 hexacyano-S,4-diazahexadienediide), the fabric becomescolored yellow to brown, depending on the particular salt used, andrinsing the colored fabric does not remove the dye. More elaboratedyeing techniques, such as are well known in the art, may be employed toheighten the color produced and to render it more permanent.

The presence of at least some water in the reaction oftetracyanoethylene with hydrazine according to this invention isessential, although in addition to water an organic solvent inert to thereactants may be employed, c. g., diethyl ether, hexane, cyclohexane andthe like. The temperature of the reaction is not critical. However, toavoid partial loss of the reactants through side reactions such aspolymerization, it is preferred to carry out the reaction attemperatures below C., and particularly below 25 C.

The foregoing detailed description has been given for clearness ofunderstanding only and no unnecessary limitations are to be understoodtherefrom. The invention is not limited to the exact details shown anddescribed. Obvious modifications will occur to those skilled in the art.

The embodiments of the invention in which anexclusive property orprivilege is claimed are defined as follows:

l. A salt of 1,1,2,5,6,6-hexacyano-3,4-diazahexadiene.

2. A compound of the 1,l,2,5,6,6-hexacyano-3,4-diazahexadienediide anionwith a cation.

3. Hydrazonium 1,1,2,5,6,6-hexacyano-3,4-diazahexadienediide.

4. A metal salt of 1,1,2,5,6,6-hexacyano-3,4-diazahexadiene.

5. A salt of l,1,2,5,6,6-hexacyano-3,4-diazahexadiene with a basic dye.

6. Process of preparing a salt of 1,1,2,5,6,6-hexacyano-3,4-diazahexadiene which comprises reacting tetracyanoethylene with onemole of hydrazine and at least two molar equivalents of a base.

7. Process of preparing the hydrazonium salt of 1,1,2,5,6,6-hexacyano-3,4-diazahexadiene which comprises reactingtetracyanoethylene with at least three moles of hydrazine.

References Cited in the file of this patent UNITED STATES PATENTS2,448,823 Popkin Sept. 7, 1948 2,762,810 Heckert Sept. 11, 19562,762,811 Middleton Sept. 11, 1956 2,762,832 Heckert Sept. 11, 1956

1. A SALT OF 1,1,2,5,6,6-HEXACYANO-3,4-DIAZAHEXADIENE
 5. A SALT OF1,1,2,5,6,6-HEXACYANO-3,4-DIAZAHEXADIENE WITH A BASIC DYE.
 6. PROCESS OFPREPARING A SALT OF 1,1,2,5,6,6-HEXACYANO3,4-DIAZAHEXADIENE WHICHCOMPRISES REACTING TETRACYANOETHYLENE WITH ONE MOLE OF HYDRAZINE AND ATLEAST TWO MOLAR EQUIVALENTS OF A BASE.